1. Field of the Invention
The present invention relates to agricultural harvesters, and, more particularly, to agricultural harvesters with concaves.
2. Description of the Related Art
An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning A combine includes a header, which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
More particularly, a rotary threshing or separating system includes one or more rotors which can extend axially (front to rear) or transversely within the body of the combine, and which are partially or fully surrounded by a perforated concave. The crop material is threshed and separated by the rotation of the rotor within the concave. Coarser non-grain crop material such as stalks and leaves are transported to the rear of the combine and discharged back to the field. The separated grain, together with some finer non-grain crop material such as chaff, dust, straw, and other crop residue are discharged through the concaves and fall onto a grain pan where they are transported to a cleaning system. Alternatively, the grain and finer non-grain crop material may also fall directly onto the cleaning system itself
A cleaning system further separates the grain from non-grain crop material, and typically includes a fan directing an airflow stream upwardly and rearwardly through vertically arranged sieves which oscillate in a fore and aft manner. The airflow stream lifts and carries the lighter non-grain crop material towards the rear end of the combine for discharge to the field. Clean grain, being heavier, and larger pieces of non-grain crop material, which are not carried away by the airflow stream, fall onto a surface of an upper sieve (also known as a chaffer sieve) where some or all of the clean grain passes through to a lower sieve (also known as a cleaning sieve). Grain and non-grain crop material remaining on the upper and lower sieves are physically separated by the reciprocating action of the sieves as the material moves rearwardly. Any grain and/or non-grain crop material remaining on the top surface of the upper sieve are discharged at the rear of the combine. Grain falling through the lower sieve lands on a bottom pan of the cleaning system, where it is conveyed forwardly toward a clean grain auger.
The clean grain auger conveys the grain to a grain tank for temporary storage. The grain accumulates to the point where the grain tank is full and is discharged to an adjacent vehicle such as a semi trailer, gravity box, straight truck or the like by an unloading system on the combine that is actuated to transfer grain into the vehicle.
In some threshing and separating systems, the rotor rotates to force the gathered crop material against rub bars of the concave as the crop material is advanced by the rotor. The force pushing the crop material into and across the rub bars creates a rubbing action that separates grain material from non-grain material, with the grain material then being able to pass through perforations between adjacent rub bars. Due to the high amount of crop material processed and contaminants such as soil and rocks also rubbing against the rub bars, the rub bars are subjected to large amounts of abrasion throughout the harvesting procedure. This abrasion wears away the rub bars of the concave and can cause wires of the concave to be exposed to the crop material, at which point the concave is considered worn out and should be replaced.
To harden the rub bars, it is known to use an induction hardening process. The rub bars, which can be made from a 1045 hot rolled plate steel, can then have a hardened case depth of 3-5 mm with a hardness of 40-45 on the Rockwell C Scale Hardness (HRC) scale. This induction hardening allows the rub bars to run for a longer period of time, but increased crop throughputs of agricultural harvesters have rendered this longer period of time insufficient. Specifically, the run time of induction hardening treated rub bars may not be the entirety of a single harvesting season, which is considered unacceptable due to the short replacement interval and the high cost of replacement parts.
It is also known to boronize components of the concave, such as the rub bars, to harden them. In the boronizing process, boron is introduced into a metal or metal alloy through a diffusion process. Typically, the component is packed with a boriding mixture and heated to a temperature of between approximately 1550 and 1750° F. so that some of the component's iron atoms (when the component is formed of iron or ferrous steel) are converted into iron boride. The boriding mixture can include boron carbide powder and potassium tetrafluoroborate as a flux material. Some disadvantages of boronizing components is that the process used is rather inflexible and labor intensive and the volume change of the component due to boronizing can be difficult to control. Further, if the boronizing process causes any undesired shape changes of the component, it is difficult to machine the component back to the desired shape.
What is needed in the art is an agricultural concave that can operate for a longer period of time before needing to be replaced and can be created in a more easily controlled manner.